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How a teenage misfit became the keeper of Julian Assange's deepest secrets - only to betray him

On a recent frigid night near Reykjavik, Iceland, Sigurdur "Siggi" Thordarson slips into a bubbling geothermal pool at a suburban swim club. The cherubic, blond 21-year-old, who has been called everything in the press from "attention seeker" to "traitor" to "psychopath," ends many of his days here, where, like most places around the city, he's notorious. But even at a spa, he can find only the briefest moment of relaxation. Soon, the local prosecutor who is trying him for leaking financial records joins him in the tub, and Siggi quickly has to flee to another pool. "How does it feel to be the most dangerous man in Iceland?" a bather shouts across the steam.

In person, Siggi's doughy shape and boyish smile make him seem less than menacing – unless you're another one of the world's most dangerous men, Julian Assange. Four years ago, just as WikiLeaks was winning international notoriety, the then-17-year-old hacking prodigy became Assange's youngest and most trusted sidekick. "It was like Batman and Robin," says Birgitta Jónsdóttir, a former WikiLeaks volunteer and member of the Icelandic parliament. But as Assange became more embattled and besieged, the protégé turned on his mentor in the most shocking of ways: becoming the first FBI informant inside the group.

Siggi's story of international espionage and teenage high-roller antics plays like James Bond meets Superbad, starring a confounding mash-up of awkward man-child and balls-out tech savant. And his tale reveals not only the paranoia and strife within WikiLeaks, but just how far the feds were willing to go to get Assange.

Siggi still lives with his parents in a nondescript high-rise, sitting at his computer in a bedroom lined with stuffed animals, including an orangutan-size Garfield he bought for $2,000. But his jet-black Mercedes ML350 is parked outside, which, along with his recent conviction for sexual misconduct against a 17-year-old boy (he says the relationship was consensual), speaks to his bizarre double life.

The revelation of Siggi's role as an FBI snitch has polarized WikiLeaks insiders. When I met with WikiLeaks spokesman Kristinn Hrafnsson (Assange declined to talk for this story), he grew red in the face, dismissing Siggi as "a pathological liar," a party line echoed by the WikiLeaks faithful. "It all sounds rather absurd," Hrafnsson says, "to go and to spend all this time analyzing the absolute bullshit that is flowing out of this young man, who is so troubled that he should be hospitalized."

While other WikiLeaks insiders also question Siggi's credibility, they insist that his story can't be discounted, and there's more to it than the organization is letting on. Tangerine Bolen, founder of the whistle-blowing advocacy organization Revolution­Truth, which used to work closely with WikiLeaks, is among those who say the group's efforts to discredit Siggi are "patently false. They're scared. The fact is Siggi played a key role in the organization and was very close to Julian."

The truth, it seems, may be held in the leaks. Siggi has provided Rolling Stone with more than a terabyte of secret files he claims to have taken from WikiLeaks before he left in November 2011 and gave to the FBI: thousands of pages of chat logs, videos, tapped phone calls, government documents and more than a few bombshells from the organization's most heated years. They're either the real thing, or the most elaborate lie of the digital age.

Assange himself validated the importance of Siggi's documents when he filed an affidavit late this past summer asserting that "the FBI illegally acquired stolen organisational and personal data belonging to WikiLeaks, me and other third parties in Denmark in March 2012" and that the FBI "was attempting to entrap me through Sigurdur Thordarson."

Whatever their origins, the SiggiLeaks are a deep and revealing portal into one of the most guarded and influential organizations of the 21st century – and the extreme measures its embattled leader is willing to take. Of all Assange's allies who've come and gone, few served him as faithfully as Siggi, or betrayed him so utterly. "One thing is sure," Siggi tells me in his thick Icelandic accent, as the vapors from the thermal pool rise around him. "I have not lived a life like a teenager."

Like Assange and so many gifted hackers, Siggi had an isolated childhood. The son of a hairdresser and a paint-company sales manager, he grew up with his little sister in a middle­class suburb of Reykjavik. Though puckish and bright, he was bored by school, alienated from his classmates and dreamed of a life beyond bourgeois Nordic comfort. "When I was, like, 12 years old, I wished for a couple of things," he tells me as we drive one afternoon past some lava fields outside the capital. "I wished to be rich; I wished to be a famous guy; I wished to live an adventureful life."

He found the excitement he craved in computers, and at age 12 he says he hacked into his first website, a local union's home page, which he replaced with a picture of "a big fluffy monkey." The experience empowered him. "When you do something like that, you feel invincible," he says, "and if you can do that, what else can you do?"

He found out two years later, when, on a plane back from a family vacation, he fixed a laptop for a businessman sitting next to him. The executive was so impressed by his skills that he offered him a job at the Icelandic financial firm Milestone: scrubbing computers of sensitive documents. Siggi figures the company trusted him with such data because he was only 14 and must have thought, as he says, "I wouldn't understand what I was supposed to delete." Plus, the pay dwarfed that of his paper route.

Curious about the files he was erasing, he'd copy them and study them at night. What he eventually discovered astonished him: Employees of Milestone seemed guilty of large-scale corruption in collusion with local politicians. At this time, in 2009, Iceland was reeling from the worldwide financial crisis, and Siggi believed the people deserved to know the role of Milestone and their dirty politicians – even if that meant leaking the files. "Someone has to do it," he thought, "and why not me?"

In the fall, Siggi says he brought more than 600 gigabytes of Milestone data to the Icelandic newspaper Dagbladid Vísir, making front-page news and leading to investigations against the politicians and businessmen he exposed. Siggi believed in the importance of exposing the corruption he describes as "illegal as it gets." With his identity still secret, he kept on leaking to other media outlets until, for reasons he never learned, his childhood friend outed him, a betrayal that changed him. "I literally just stopped believing in humanity," he says. "Since then, I just basically stopped having feelings."

But after being arrested and splashed across the news, he found a powerful connection in Kristinn Hrafnsson. A well-known TV reporter in Reykjavik at the time, Hrafnsson considered Siggi's leaks to be "quite significant" and worthy of an introduction to another up-and-coming whistle-blower, Julian Assange, who was speaking at the University of Iceland. Though WikiLeaks had already exposed death squads in Kenya and financial malfeasance in the Swiss bank Julius Baer, the group was still largely unknown. But at the panel, Siggi found, to his surprise, that Assange was well aware of his work – he even chastised the reporter who revealed Siggi's name in the Milestone leak. "He was basically just condemning the guy, sayingouting whistle­blowers is wrong," recalls Siggi, who reveled in the support.

The bond between the two was immediate. Assange too had been arrested for hacking when he was a young man in Australia. He also had a son, Daniel, who was roughly Siggi's age, whom he had little contact. "I think Julian saw himself in Siggi," says Jónsdóttir. "Julian felt an immediate sympathy toward the kid."

After the panel, Siggi says he took Assange to Sea Bar, a small, rustic restaurant on the water. Over lobster soup and whale steak, they spoke about politics, hacking and their shared sense of purpose in exposing the secrets of the elite. Assange struck Siggi as someone with the courage to take on anyone. "He's the kind of activist that does the thing that has to be done," Siggi tells me. After talking for a few hours, Assange took out a small metal box. "Have you ever seen this before?" he said.

Assange cracked open the container and revealed three phones inside. "These are encrypted cellphones," he said. "I'm going to give you one. Just keep it on at all times so I can communicate with you, day and night."

Within just a few weeks, Siggi was inside Assange's small inner circle, a complex place where decisions centered on the mercurial leader. "There's a video I want to show you," Siggi recalls Assange telling him as they sat inside Jónsdóttir's small house in Reykjavik one wintry night soon after they met in February 2010.

"Are you sure you want to show this to him?" said Jónsdóttir. She was concerned about Siggi's involvement in the project and didn't entirely trust him, but nevertheless felt protective of the boy. "He was just a lonely kid that had been bullied," she recalls, "and I felt sort of motherly towards him in the beginning." Before Assange cued up the clip, she warned Siggi, "This is a disgusting video."

The grainy footage showed an Apache helicopter firing upon men in the streets of Baghdad. "This can cause a World War III," Assange said. Though Siggi was new, he didn't hesitate to express his concerns. "We have to be careful about what we publish," he said. When Assange wanted to call the video "Collateral Murder," Siggi told him he thought that was too dramatic. Assange seemed to value the bluntness of his new recruit. "I considered him a friend, and I believe he considered me a friend as well," Siggi recalls. "If I was against something he said, I told him so, and that was something he liked."

That spring, when the group was riding an international wave of attention after the video's release, Siggi, whom Assange gave the handle PenguinX (he was later known as Q), became his dependable errand boy and confidant: talking regularly, looking for equipment, making encrypted calls to contacts on Assange's behalf. After Bradley Manning was arrested for the "Collateral Murder" leak in May 2010, Assange wrote Siggi that it "might help if people think he's gay. . . . [The] gay lobby in U.S. is very big, and the whole 'gays in the military' thing is very contentious." When Assange eclipsed pop stars in Time's person-of-the-year poll, he giddily messaged Siggi, "We beat Gaga!" But the pressure was getting to Assange. In a chat on July 7th, 2010, Siggi asked Assange how he was doing amid all the controversy. Assange replied, "Stressed."

"Anything i can do to loose some stress?" Siggi typed.

"Find me a pretty girl with lots of warm olive oil;)" Assange replied. But women, too, soon became part of Assange's worries. One night in August, Siggi's cryptophone rang with a call from Assange. "Can I trust you?" he said.

"Definitely," Siggi replied.

"Interpol is most likely going to issue an arrest warrant for me."

Two women in Sweden alleged he had committed rape and sexual harassment, which Assange denied, saying sex with each was consensual. "The best solution to all this mess might just be going to Sweden and finishing the interrogation," Siggi told him. But Assange pushed back, saying the U.S. would try to extradite him. "If you get arrested, I'll just have a backup plan of stealing you from the police," Siggi said in all seriousness.

But by fall, Assange had other problems: the defection of his closest supporters. His controlling nature had grown overbearing. Hacktivist Daniel Domscheit­Berg, Jónsdóttir, journalist Herbert Snorrason and others in the small group of insiders battled with Assange over his reluctance to redact the Afghan war logs, which, they feared, would put lives at risk. Jónsdóttir spoke out to the media, calling for Assange to step aside and "let other people carry the torch."

And Assange's confounding closeness with Siggi, which bordered on a paternal relationship, was also an issue. "The perception was that Siggi basically got to a level where Julian trusted him in a matter of days," says Snorrason. The core volunteers considered Siggi a dangerous liability, prone to youthful indiscretions and lies. But, as Domscheit-Berg recalls, the rumors were being stoked by Assange himself. "Julian told us we shouldn't speak to Siggi because he couldn't be trusted," he says. "He told me Siggi was a notorious liar, but then again Julian told people I was a notorious liar probably because he's a notorious liar. I think it's psychological. We knew Julian was dealing with Siggi all the time – it all implied Julian was using him. These are all kinds of games children get into."

Jónsdóttir was among those caught in Assange and Siggi's web. "I told Julian, 'There's something weird, I can't explain it, but I have this feeling,'" Jónsdóttir recalls. "'You just be very careful with this guy.' But he didn't believe me." Though she continuously tried to get Siggi removed from projects, Assange stood by the boy. "He might have trusted him with something that he didn't want him to expose," she says.

For Siggi, there was a simple reason he rose in Assange's eyes: the old guard's weakness. "To be blunt, they were just cowards," he says. "I stayed with Julian through this entire shit. I didn't leave, so that's probably why he started to trust me more – I showed him loyalty."

According to the chat logs, Assange commanded Siggi to insinuate himself with Jónsdóttir, in light of her calls for his resignation, and report back. "But be careful," Assange warned Siggi. "She is good at smelling lies that are intellectual, though not so good at smelling emotional lies." Days later, after Siggi returned with updates on Jónsdóttir, Assange wrote to him, "Good work on B." Siggi suggested Assange confront her in person, to which Assange replied, "I will, but I need to let my anger cool, or it would be with a gun."

Worried that logs of him discussing the rape allegations could be released by Snorrason, Assange told Siggi to hack into the journalist's computer and remove them. "The log, get rid of it," Assange wrote. "His pc must be taken over, and that deleted."

"How can we delete it from his computer?" Siggi replied. "We would need physical access to his computer." Assange said he could be fooled into downloading a trojan, a kind of computer virus. Though they never hacked Snorrason, the schism within WikiLeaks was tearing the group apart. That fall, Domscheit-Berg, Jónsdóttir, Snorrason and others left. But Siggi remained, and he wanted to make sure that Assange understood his dedication. "What about me?" Siggi wrote him late one night in a chat. "Any trust issues at all?"

"No. I know your difficulties and I accept them," Assange replied. "Good intent and loyalty is more important to me."

By October 2010, Assange had appointed Siggi to Snorrason's old post of running the WikiLeaks chat room. It was an important position, vetting the faceless flood of potential allies and leakers, and passing along the cream to Assange. "Keep your eye open for people trying to befriend you or others in an attempt to infiltrate WikiLeaks," Assange instructed him in a chat. "Lives depend on your diligence."

Assange was on the lookout for FBI agents, informants and betrayers. And there was one unlikely group of people whom he feared might be rallying against him: the Bradley Manning Support Network. In July, Assange had pledged to pay for a substantial amount of Manning's defense, which was expected to cost more than $100,000, and the group was increasingly angry that, months later, no money had come through. According to Siggi, Assange had simply moved on.

Throughout the fall, Siggi was getting word from BMSN co-founder David House that David Coombs, Manning's attorney, was threatening to go public. "Coombs will go to the media very soon," House warned Siggi in one chat. "I need someone in WL to do their job and actually start giving a shit about Manning's defense."

But WikiLeaks went on the offensive instead. "Julian wanted to know everything they were doing," says Siggi. On October 7th, Siggi hacked into a Skype conference call of the BMSN and sent the recording to Assange. In the wee hours of November 11th, with word of another Skype call that evening, he asked Assange if he should do it again. "Do you want me to record the BMSN conference?" Siggi wrote.

"YES," Assange replied.

"Oki dok:)"

The next night, Siggi reported back: Mission accomplished. "Yey the Recording was successful," he typed in chat. "Want me to upload and send to you?"

"Yes. But going to bed now," Assange wrote. "Good work on the record."

"Ok:) Did you remember to brush your teeths:)"

With still no funds by December, the BMSN did go public, resulting in unflattering headlines, like The Washington Post's "WikiLeaks hasn't fulfilled financial-aid pledge for suspect in leaks." (Eventually, the group gave $15,000.)

But by the end of 2010, Assange had sought refuge from the Swedish case by retreating to Ellingham Hall, a country mansion in England owned by dilettante investigative journalist Vaughan Smith. Assange deployed the now-18-year-old Siggi as one of his few trusted couriers for WikiLeaks' most prized and explosive leaks of all – the quarter-million diplomatic cables from Manning – which they were delivering to news outlets around the world. "Do you have an EU passport?" Assange messaged Siggi one night.

"Yes Why:)?"

"Just thinking about various meetings."

When I met with WikiLeaks spokesman Hrafnsson, he insisted that apart from a trip to Ellingham Hall Siggi "was never traveling on behalf of WikiLeaks anywhere." But several European journalists I spoke with confirmed their meetings with Siggi, and some insisted that both Assange and Hrafnsson were well aware. "Kristinn told me Siggi was the one to deal with," says Leonie van Nierop, a reporter for a Netherlands daily paper, NRC Handelsblad, who met with Siggi in Amsterdam. "Siggi was constantly on the phone with Assange," says Dan Sommer, the former head of security for the U.S. Embassy in Reykjavik and a local pastor, who traveled as Siggi's bodyguard. "It was clear that Assange knew what Siggi was doing."

Assange had potential publishers vetted in person before giving them the files, and Siggi was among those tasked with the job, arriving in each city with an encrypted thumb drive containing excerpts from the cables. The twisted humor of the transactions – that the biggest leak in U.S. history was being delivered by a baby-faced 18-year-old – wasn't lost on the reporters and editors with whom Siggi met. Dutch journalist Eelco Bosch van Rosenthal found him to be "an insecure guy who wanted to be something in the world."

After spending several days with Siggi, van Nierop took a liking to the boy. She had acted as a tour guide for a day, leading Siggi through the famed red-light district in Amsterdam, where she noticed that he didn't seem very intrigued by the women offering themselves in windows. "He was more interested in the trains in the station than the hookers," she recalls. She could tell, while listening to her colleague speak with Assange about Siggi after the trip, that the two were geeky pals. She says Assange teasingly said that since she "took Siggi to the red-light district, couldn't you have bought a girl for him?" Van Nierop thought Siggi's relationship with Assange also explained why the boy seemed isolated. "If Julian Assange is your best friend," she says, "you must be a little lonely."

With media outlets often paying his way, Siggi says he was "having the time of my life." When he told his parents he was traveling on missions for WikiLeaks, they balked; but as his father told me, "He was 18. There was nothing we could do." In January 2011, he arrived in Honduras to meet with editors from the newspaper El Heraldo and was greeted by a team of armed bodyguards. When Siggi asked why he needed such heavy security, one of the goons told him, "because you're white, and you could get stabbed or kidnapped."

But Sommer, his personal bodyguard on many of the trips, couldn't get the boy to leave behind his childhood. At every city, Siggi insisted on taking time out to visit the local waterpark and eating McDonald's. In Budapest, Siggi had Sommer take him to his first strip club. In New York, Siggi wanted to try out a pepper-spray pen his bodyguard bought at a local spy shop. Back at the hotel, a half hour before a meeting, he persuaded his bodyguard to shoot him with it to see how it felt – but vastly underestimated the burn. "It was horrible," says Siggi, who had to douse himself with milk to relieve the pain. He showed up at his next meeting with bloodshot eyes and a rash. "We had to explain that I wasn't stoned," Siggi says.

While in Washington, D.C., he had one mishap that was too close for comfort. His bodyguard was driving a Jeep the wrong way down a street by the Pentagon, when he saw a police car pull out nearby. With the diplomatic cables in the back seat, Siggi freaked. "Fuck me!" he said. "Oh, my God, we could get pulled over. We're gonna go to Guantánamo Bay!" But as luck would have it, the police car passed him – missing the chance for the bust of a lifetime.

During the half dozen times Siggi arrived at Ellingham Hall to visit Assange, he says he knew what to bring with him: a suitcase full of Malt Extrakt, Assange's favorite Icelandic soda. "I saw it in his face," Siggi says, "somebody actually thought about him. He was happy that I remembered."

Despite his circumstances, Assange was enjoying the comforts of mansion life and the companionship of his close-knit circle of supporters, including Siggi. They went swimming in the nearby lake, had long dinners in the regal dining hall. At Assange's blowout 40th-birthday party, Siggi got drunk for the first time, on licorice schnapps, and drove his car into a ditch during a midnight junk-food run. "It was hilarious!" Siggi recalls.

But in private moments, Assange told Siggi that the political and personal battles were wearing on him. "He said that he was really tired," Siggi says. "I'd just like to give up," Assange told him.

As the increasingly besieged WikiLeaks leader's profile grew, so did his paranoia. Assange asked his protégé to write up psychological profiles of WikiLeaks core members. Siggi, however, initiated more recon on his own. Late one night, he clandestinely cloned their hard drives, including the laptops of Hrafnsson and longtime associate Sarah Harrison, and he provided Assange with a report of their contents.

Though Assange hadn't asked him to do this, Siggi claims he read the findings and Assange allowed him to continue snooping during visits to Ellingham Hall. At one point, Siggi says, Assange asked him to search through the computers of Vaughan Smith, the journalist who owned the home, because he thought Smith was secretly video­taping him. Siggi sneaked into Smith's office, rifling through his things until he found computer-memory cards and drives, which he promptly began wiping clean. I ask Siggi if he felt that spying on the volunteers and their host was wrong. "Privacy is just a myth, you know," he replies. "It doesn't really exist."

But Assange's spy games grew worse. BMSN co-founder House told Wired that Assange asked him in January 2011 to swipe a copy of former insider Domscheit-Berg's WikiLeaks exposé prior to publication. Around the same time, Siggi claims Assange asked him to set up hidden cameras to spy on guests inside Ellingham Hall. "Julian just had this idea that everybody was after him," he says. "He wanted this to be done. It made him feel more secure." Siggi bought coat-hook spy cams and affixed them on the back of doors throughout the house, including bedrooms. He says he also installed a spy cam in a room used for meetings with visitors like Eric Schmidt of Google and Steve Kroft of 60 Minutes.

When I call Smith to ask him if he had ever seen any of these items in his house, he said he recalled finding a coat hook in a box and wondering why it was there. "I remember thinking, 'That's weird,'" he says. "'Why would someone bring a coat hanger into my house?'"

Siggi's infiltrations soon spiraled well beyond Ellingham Hall. While WikiLeaks has always maintained that they are, as Hrafnsson puts it, "passive recipients" of leaks, Siggi spent much of 2011 conspiring with the most renowned hackers on the Net. The operation fulfilled what was now a common pattern: Siggi going rogue but with what he said was his boss's tacit approval. "I understood what Julian wanted," Siggi says.

In the wake of the Manning cables, Assange wanted more newsmaking leaks, but the material coming in wasn't meeting his insatiable appetite or ambitions. So Siggi reached out to Gnosis, a hacker group that made its name in December 2010 for compromising more than a million registered accounts on Gawker websites.

Gnosis tipped Siggi off to a notorious 16-year-old female from Anonymous named Kayla who had just helped hack HBGary, an IT security firm that worked for the U.S. government. Gnosis claimed to have an unpublished copy of HBGary's database, including its clients' names and e-mails. "Don't release it," Siggi messaged back. "Allow us."

Anonymous, however, ended up leaking the files themselves, and Siggi told Gnosis that his boss was pissed. "You can't really control Anonymous," Gnosis replied. "You can kinda herd them in the right direction but other than that lol good luck."

But that didn't stop Siggi from trying. In January 2011, Siggi got word that DataCell, the hosting service behind WikiLeaks, had valuable contracts pulled by an Icelandic power company called Landsnet, and he wanted revenge. "I have a funny request for you," Siggi wrote Kayla in one chat. "www.landsnet.is is something 'Anonymous' should take down if it's possible." Two minutes later, Kayla replied that she'd just unleashed a botnet against the website, a form of a cyberattack that swamps the site with requests. Siggi tried logging on to the Landsnet site. "Haha request timed out," he wrote.

The attack didn't stop there. When Siggi explained that the Icelandic government had made a deal to assume DataCell's contracts, Kayla asked if he wanted her to take down one of its sites too. "Definitely," Siggi replied. Minutes later, a ministry site was down. But as the sites fell, Siggi joked that Kayla might inadvertently knock Iceland's power offline too. "If you see a button that says turn off electricity don't press it please," he wrote.

With his connections to the Anonymous cell more secure, Siggi suggested that the group could be of even greater help – getting them more secret documents that WikiLeaks could release. "I don't care where the information comes from," Assange had told him, which Siggi took as carte blanche to solicit stolen material. So Siggi had Gnosis introduce him to one of the most infamous hackers of all: Sabu, leader of the Anonymous offshoot LulzSec. In the spring of 2011, LulzSec had taken down the sites of high-profile targets including Fox, the CIA and PBS, whose Web page they replaced with the title "FREE BRADLEY MANNING. FUCK FRONTLINE!" But Sabu wanted proof that Siggi was who he said he was by speaking with Assange directly. Siggi claims to have complied and arranged the Skype call.

With Sabu convinced, Siggi put him on a job: to dig further into the Icelandic government's computers to see if it had intel on the DataCell deal. Soon, Sabu delivered. Siggi says Assange told him to have LulzSec upload the files to a WikiLeaks FTP server, which they did. And Sabu soon had more secrets to offer. He told Siggi his crew had recently hacked Stratfor, a "global intelligence" agency and government contractor, and found more than 5 million confidential e-mails between Stratfor and companies such as Dow Chemical, Lockheed Martin and Northrop Grumman, as well as government agencies including the Department of Homeland Security and the U.S. Defense Intelligence Agency.

But as the e-mails poured in, Siggi began to grow anxious and questioned the scale of the operation. Even though he was the one who initiated the relationship with the hackers, he worried that they were going too far. "Crossing this line by accepting stolen information and publishing this is literally just breaking the law," he says he told Assange. "You're going away from being a journalist organization and threatening national security." But, once again, Assange told him he didn't care how the information was obtained.

Back at home in his bedroom, Siggi couldn't sleep. He lay in bed imagining the FBI breaking down his door, storming into his house, past his giant Garfield doll, his sleeping parents and his little sister, and hauling him off to Gitmo for good. For months, he'd had insomnia, but now his mind and heart were racing like never before. When he did manage to fall asleep, he woke up screaming.

Just after 3 a.m. on August 23rd, 2011, the pressure Siggi felt finally broke him. Crawling from bed, he e-mailed the U.S. Embassy in Reykjavik and asked for a meeting. It wasn't just the LulzSec association that concerned him. Assange seemed to have changed from the man he met the year before. While he was unwilling to donate the amount he'd promised to Manning's defense, he was ready to blow large sums rehabilitating his ailing image. "I don't care," Assange told him. "We have a million bucks, and we can spend it on buying publicity." For Siggi, it was a turning point. "I realized that this wasn't the same ideology as before," he says. But truth is, Siggi was also trying to save his own ass. Going to the FBI, he hoped, would inoculate him against prosecution. And, he admits, he thought being a spy for the feds would be a thrill. There was just one price to pay: "I would be betraying WikiLeaks, Julian, my friends," he says.

The next day, Siggi got called to the U.S. Embassy and was soon taken to a nearby hotel, where he was met by the FBI. They wanted to know WikiLeaks' physical security, their technical security, locations of computer servers, how Assange lived, his daily routine, "literally, everything," Siggi says. And he had plenty of data to share: several hard drives of WikiLeaks private files that he had amassed during his time with the organization – just in case he ever needed them.

Signing a nondisclosure agreement, he spoke daily with the FBI, passing along the chats he was handling, the leaks that were in negotiation. And, as he told the FBI, there were big ones to be had, courtesy of Sabu. As they were getting the Stratfor files from LulzSec, Siggi had heard that Assange was trying to get Sabu to join the WikiLeaks team. "Did J say anything about recruiting you permanently?" Siggi asked Sabu in one chat.

"Well he emailed me once but we didn't get to talk," Sabu replied. "Guess he's been busy/careful or whatever but let him know we have intercepted 92GB of mails from .gov.sy so this can be one of the biggest leaks in history." In November 2011, Sabu began passing excerpts of this data, later published by WikiLeaks as the "Syria Files," to Siggi – 2 million internal e-mails, going back to 2006, from companies, politicians and ministries in Syria. According to Siggi, when he told Assange about the new information, "He said, 'OK, cool,'" Siggi recalls. "'They can upload it.'"

But Siggi's spy work was jeopardized that same month when he got an angry call from WikiLeaks' spokesman Hrafnsson, accusing him of embezzling $50,000 in proceeds from selling WikiLeaks merchandise online. Siggi insists that he had run the money through his account with Assange's permission, and that any extra cash went to cover his own expenses. With both sides warring, it isn't clear whom to believe. But even if Siggi was guilty, the accusations raised more questions about why the boy, whom the group says had no role in the organization, had access to such funds in the first place. Hrafnsson threatened to report him to the police. Siggi e-mailed the FBI telling them the news. "No longer with WikiLeaks – so not sure how I can help you more. Sorry I couldn't do more :("

To his surprise, the FBI still had more work for him. Shortly after WikiLeaks published the Stratfor files in February 2012, Siggi was flown to Washington, D.C., where he met with members of the CIA, the DOD and the FBI at a Marriott hotel. The questions became dizzying: They wanted to know about others besides Assange – Jónsdóttir, Hrafnsson and more.

It didn't take long for the hammer to fall. On March 5th, LulzSec hacker Jeremy Hammond was arrested for hacking the Stratfor files leaked to WikiLeaks (he'd later be sentenced to 10 years in prison). The next day, Kayla, the LulzSec hacker Siggi had conspired with, was indicted on conspiracy charges – and revealed to be a man, 25-year-old Ryan Ackroyd, from England. But the biggest shock came when Siggi read in the news that Sabu was an FBI informant, and had been since June 2011. It suddenly all made perfect sense. For months, he had been informing the FBI of his conversations with Sabu, and they hadn't seemed to care. And since Sabu had been an informant during the time of the Stratfor and Syria files, that meant something incredible: The FBI had been well aware of the Stratfor and Syria hacks all along, and done nothing to intervene. Their target had always been Assange. The biggest and most famous hack in recent years was a carefully built plot by the FBI to snare a man it considered as an enemy of the state.

"Ultimately, the FBI's mission is to apprehend criminals and prevent the commission of serious crimes," says Glenn Greenwald, the journalist whom Edward Snowden leaked NSA files to last year. "In this particular case, they purposely allowed the commission of serious crimes they could have easily stopped. To treat an American firm like Stratfor and the privacy of Syria as sacrificial lambs in a campaign to entrap Julian Assange into criminality is unbelievably radical – you can even say corrupt."

During a meeting in Denmark in March, the FBI had Siggi sign over eight hard drives containing his WikiLeaks files. When Siggi asked them about Sabu, the agents just smiled and gave him $5,000 to cover his cost of living, then sent him on his way. He never heard from them again.

In January 2013, Siggi watched TV in horror as Hrafnsson told a reporter how he had learned the previous summer that the FBI had come to Iceland to secretly interview someone about WikiLeaks – he just didn't know who it was. But after meeting with Ögmundur Jónasson, who had just left the position of Iceland's Minister of the Interior, he pieced together that Siggi was the one who had gone to the FBI.

I met with Jónasson, who told me how, in June 2011, Iceland received a warning from U.S. authorities of "an imminent attack on Icelandic computer systems." Two months later, Jónasson found out that a plane full of FBI agents had arrived in Iceland for another purpose: to investigate WikiLeaks. Because they didn't have authorization for this, he turned them away – only to find out later that they had taken Siggi to Copenhagen. "I still have suspicion," he says, "that this was part of an attempt to put a case against Julian Assange."

Hrafnsson remains just as outraged, though he tells me he and Assange weren't shocked. "We have stopped being surprised about anything," he says. When I ask if Assange feels betrayed by Siggi, Hrafnsson arches his brow. "Inherently in your question is the assumption that there was a very close relationship, which I never saw."

While Assange remains holed up in the Ecuadorian Embassy in London, Siggi faces the repercussions of coming clean. Among other things, for the first time in this story, he's admitting to the Milestone leak. "It's probably going to lead to my conviction," he says. "But I just have to face that." In the meantime, in addition to unrelated fraud charges, he's appealing his sentence of eight months for sexual misconduct. Siggi claims the victim's father pressed the charges after learning of Siggi's relationship with his son; Siggi calls his homosexual tryst a "phase."

As for WikiLeaks, should he ever get asked one day to testify against Assange, Siggi isn't sure whether he will comply. He knows that he betrayed his former mentor and friend. But he says he did it all for the very same reasons he believed in WikiLeaks and Assange: "The truth needs to come out."